Digital micro-mirror devices (also referred to as deformable mirror devices or simply DMDs) are finding many uses in light deflecting technologies. In operation, the devices are akin to small mirrors which rotate about a fixed axis. The rotation causes light to be deflected under control of the rotation. Thus, in an array of DMDs each device, or pixel, can be selectively rotated thereby patterning light reflected from the array.
Digital micro-mirror devices can be used in a wide variety of applications. These applications include displays such as television (e.g., high definition television), computer monitors and other video displays. An example of a video display system is disclosed in U.S. Pat. No. 5,079,544. The DMDs can also be used in printer applications including printers, photocopiers and facsimile machines. An example of a printer system is disclosed in U.S. Pat. No. 5,101,236. Further, DMDs can be used in other applications including video cameras.
A full-color projection display is typically implemented by simultaneously projecting the images of three light modulators, one for each of the primary colors--red, green and blue. If however the light modulator can be addressed fast enough, it is possible to implement a full-color projector with a single modulator and an illumination system that sequentially delivers red, green and blue light to the modulator, such as a rotating color wheel. In this system, the projected color fields are integrated by the eye over the frame time to form the full color image.
Since the digital-micromirror device (DMD) modulator can be addressed fast enough to implement the field sequential system, this method is typically preferred due to the reduced amount of system hardware. However, the single light modulator system can project only about one third of the total lumens to a screen that a three modulator system can. As a result, the range of applications for single modulator systems is limited.
In addition, the field sequential projector has several artifacts that are associated with the different color fields being projected at different times. As an example, these artifacts may cause moving objects on the screen to appear fringed around the end to one looking at the screen. Finally, there are certain lamps that are used for projection systems that do not have proper color balance, i.e., they are deficient in one of the three primary colors. Both single modulator and three modulator systems must sacrifice some of the total brightness in order to color balance a system using this type of lamp.